Semiconductor integrated circuit fabrication facilities (“Fabs”) are highly automated. An automated material handling system (AMHS) is used to transport semiconductor wafers between various process tools. The wafers are generally held in a storage container such as a front opening unified pod (FOUP). Nitrogen and other inert gases are used to prevent oxidation of wafers in the FOUP. When nitrogen and other inert gases are purged into the FOUP, some particles in the nitrogen and inert gases may also be introduced into the FOUP and cause damage to the wafers. Therefore, a filtering cartridge is disposed on the FOUP for preventing the particles from entering the FOUP.
The filtering cartridge has a limited service life. If the filtering cartridge is damaged, the particles in the filtering cartridge may enter the FOUP. Therefore, the filtering cartridge is required to be inspected and cleaned or replaced when the amount of particles therein reaches to a certain amount. Conventionally, the filtering cartridge is visually and manually inspected by an operator, thus resulting in a lot of labor costs. On the other hand, the conventional manual particle inspection is not linked to a statistical process control (SPC) system, and thus the SPC system lacks of timely particle information in the FOUP to perform quality control.